Optimized Nitridation of Al[sub 2]O[sub 3] Interlayers for Atomic-Layer-Deposited HfO[sub 2] Gate Dielectric Films

gate dielectric thin-film stacks were atomic-layer-deposited on HF-cleaned Si wafers. The 2.3 nm thick interlayer was treated under an atmosphere at 790°C for 40 s with and without rf plasma prior to a 4 nm thick film deposition. Plasma nitridation increased interlayer thickness by 0.9 nm and decreased overall capacitance, whereas thermal nitridation did not, and overall capacitance was the same as that of a nontreated stack. The thermal stability of the capacitance density and flatband behavior were also improved by thermal nitridation of the interlayer. Furthermore, nitridation of the interlayer greatly reduced the interface trap density of the samples.